The two grips and two end caps in black come to about $528. You won't need to buy a new throttle by wire sensor assembly since the same part number was used on your 2017 model. The right hand grip just plugs into the existing sensor. As for the Harley kits, they may never make a kit available with the exact same grips they used in production. That has been the case on some older models. If you really want those grips soon, you may have no choice but to buy the production parts. Btw, there are more than a few SESG owners on the site who have purchased and installed production grips instead of one of the available kits, so you will have some experienced resource people available if you decide to use the production parts. Fishing the wires for the left grip through the bars will probably be the hardest part of the process.
Jerry